Radio Base Station Apparatus and Mobile Terminal

1. A radio base station apparatus comprising: a modulation section configured to modulate a control signal of a first mobile communication system with a first system band, and a control signal of a second mobile communication system with a second system band which is relatively narrower than the first system band to obtain a modulation signal; a control signal allocating section configured to allocate the modulation signal to a control channel element (CCE) of at least one frequency band having the second system band as a unit, according to a predetermined rule; an interleaver configured to interleave the modulation signal for each frequency band; and a mapping section configured to map the interleaved modulation signal to time/frequency domain, wherein the first mobile communication system and the second mobile communication system overlap, CCEs of each frequency band are assigned with respective numbers, the predetermined rule is a rule for allocating a control signal for a specific mobile terminal, to a CCE having a same number in each frequency band or a rule for allocating a control signal for a specific mobile terminal, to a CCE within a CCE range indicated by a same number in each frequency band, when the control signal for the specific mobile terminal is allocated to the control channel element (CCE) within the CCE range indicated by the same number in each frequency band, a number of CCEs to allocate the control signal is variable within the CCE range.

2. The radio base station apparatus according to claim 1 , wherein, when the control signal for the specific mobile terminal is allocated to the control channel element (CCE) within the CCE range indicated by the same number in each frequency band, the mapping section is configured to perform mapping for each frequency band.

3. The radio base station apparatus according to claim 1 , further comprising: a quality determining section configured to determine reception quality of a signal from a mobile terminal, wherein the control signal allocating section determines the number of CCEs to allocate the control signal, in correspondence to the reception quality determined by the quality determining section.

4. A mobile terminal comprising: a demapping section configured to demap signals in time/frequency domains, the signals being transmitted from a radio base station apparatus; a deinterleaver configured to deinterleave the demapped signals for respectively frequency bands; and a demodulation section configured to demodulate the deinterleaved signals according to a predetermined rule, and to determine whether a control signal is addressed to the mobile terminal, wherein the deinterleaved signals are modulation signals of a control signal of a first mobile communication system with a first system band and a control signal of a second mobile communication system with a second system band which is relatively narrower than the first system band, and the first mobile communication system and the second mobile communication system overlap, each of the modulation signals is allocated to a control channel element (CCE) of at least one frequency band having the second system band as a unit, CCEs of each frequency band being assigned with respective numbers, the predetermined rule is a rule in which the mobile terminal demodulates CCEs having a same number in respective frequency bands all at once, and determines whether a control signal is addressed to the mobile terminal or a rule in which the mobile terminal demodulates CCEs within a CCE range indicated by a same number in each frequency band, and determines whether a control signal is addressed to the mobile terminal, and when the control signal for the specific mobile terminal is allocated to the control channel element (CCE) within the CCE range indicated by the same number in each frequency band, a number of CCEs to allocate the control signal is variable within the CCE range.

5. A mobile communication system comprising: a radio base station apparatus having: a modulation section configured to modulate a control signal of a first mobile communication system with a first system band, and a control signal of a second mobile communication system with a second system band which is relatively narrower than the first system band to obtain modulation signals; a control signal allocating section configured to allocate each of the modulated signals to a control channel element (CCE) of at least one frequency band with the second system band as a unit, according to a predetermined rule; an interleaver configured to interleave each of the modulated signals for each frequency band; and a mapping section configured to map the interleaved modulation signals to time/frequency domains; and a mobile terminal having: a demapping section configured to demap signals in time/frequency domains, signals being transmitted from the radio base station apparatus; a deinterleaver configured to deinterleave the demapped signals for respectively frequency bands; and a demodulation section configured to demodulate the deinterleaved signals according to a predetermined rule, and to determine whether a control signal is addressed to the mobile terminal, wherein the first mobile communication system and the second mobile communication system overlap, CCEs of each frequency band are assigned with respective numbers, the predetermined rule is a rule for allocating a control signal for a specific mobile terminal, to a CCE having a same number in each frequency band or a rule for allocating a control signal for a specific mobile terminal, to a CCE within a CCE range indicated by a same number in each frequency band, and when the control signal for the specific mobile terminal is allocated to the control channel element (CCE) within the CCE range indicated by the same number in each frequency band, a number of CCEs to allocate the control signal is variable within the CCE range.

6. The radio base station apparatus according to claim 5 , further comprising: a quality determining section configured to determine reception quality of a signal from a mobile terminal, wherein the control signal allocating section determines the number of CCEs to allocate the control signal, in correspondence to the reception quality determined by the quality determining section.